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About the project

Scottish and Southern Electricity Networks (SSEN) and Balfour Beatty have successfully energised the connection for Dorenell wind farm in Moray. The wind farm connection, which will add capacity for a further 220 MW of renewable energy to the GB transmission system, has seen the deployment of composite poles, the first time this innovative technology has been used on the GB transmission system.

In the adjacent video, SSEN Lead Project Manager, Paul Higginbotham discusses the innovative solution developed with Balfour Beatty and the successful delivery of the project.

The aim of the project was to provide a connection for Dorenell Wind Farm to the transmission network at Blackhillock Substation (near Keith)

The connection comprises one double circuit 132kV composite “H” pole overhead line running over a distance of approximately 22 km in length. The project was successfully energised in September 2018.

Progress gallery

Please have a look through the progress gallery to view the development of the project. If there are any elements of the project that you would like to see here, please get in touch.

Design

The overhead line design utilises composite “H” poles, which are made out of fibreglass/reinforced polymer and are grey in colour. These composite structures have been used successfully for the last 20 years or so in Canada, USA, Scandinavia and Ireland for transmission, distribution and communications networks.

Due to the way the electricity network in the UK has been developed there has been little incentive for Network Operators to do anything different than standard wood poles and steel lattice towers for the last few decades. Ofgem, the Government regulator for electricity and gas markets has recently laid out a framework to incentivise Network Operators to innovate, providing improvements in the security of supply and reducing costs for energy bill payers. The Dorenell Wind Farm connection has been able to take advantage of this change, enabling the project team to drive this new technology to bring environmental and cost benefits.

This proposal brings the following benefits:

Composite poles are stronger than wooden poles, which allow them to support a larger sized conductor on one overhead line. Wood poles would require two parallel lines. This helps to reduce the visual effects of the overhead line and minimise land take.

Although they are taller than wood poles at 24 m in height (rather than 16 m), they will allow for a greater clearance underneath the conductors, allowing for agricultural machinery to continue to operate safely beneath the overhead lines.

A greater spacing between individual poles can be maintained, at a distance of approximately 180 m between poles, compared to 80-100 m for wood poles. When combined with the single overhead line design this will reduce the number of poles required for the connection by 75%, greatly reducing a burden upon the land. This will reduce the impact upon the use and operation of the land surrounding the overhead line.

The composite poles allow for a reduced construction programme. For this project the current programme duration is approximately 12 months overall.

A single line of composite poles has a reduced corridor width when compared to the double line of trident poles.

The composite poles are easier and less expensive to maintain and have a life expectancy of 80 years rather than 40 years for wood pole, meaning less maintenance visits.

Why is the project required?

As the transmission licence holder in the north of Scotland we have a duty under Section 9 of the Electricity Act 1989 to facilitate competition in the generation and supply of electricity. We have obligations to offer non-discriminatory terms for connection to the transmission system, both for new generation and for new sources of electricity demand.

The aim of the project was to enable renewable energy to connect to our transmission network. Under our Network Operators Licence this connection should be efficient, co-ordinated and economic, whilst having the least possible impact on the environment.

Legend

The data in this map is provided for indicative purposes only and may be subject to change. Scottish Hydro Electric Transmission plc do not accept responsibility for its accuracy, completeness or validity. The data should not be copied, reproduced or utilised externally without permission.

Investments in projects are made by SHE Transmission plc. Electricity transmission companies are authorised to recover the costs of such investments through 'use of system' charges which are levied by National Grid Electricity Transmission plc on generators and suppliers of electricity. Suppliers recover their costs from all electricity customers. In order to protect the interests of customers, the transmission companies have to demonstrate to the energy regulator, Ofgem (Office for Gas and Electricity Markets) that proposed investments are necessary, are efficient and are economical so that the charges which are ultimately levied on all electricity customers are justified.

This means SHE Transmission is subject to a funding mechanism established by Parliament and regulated by Ofgem. Cross subsidies between different businesses in the SSE group is not permitted.

The Scottish Ministers are responsible for determination of applications submitted under Section 37 of the Electricity Act 1989. Both statutory consultees and members of the public have the right to submit their representations on the application. All representations will be considered by Scottish Ministers in their determination of the application.The Office for Gas and Electricity Markets (Ofgem), as the regulator, has to approve all investment so project proposals are developed under license conditions. Preferred route corridors chosen will comply with revised ‘Holford Rules’ which are the recognised industry approach to routeing overhead lines amended to reflect Scottish circumstances.

The Holford Rules originated in 1959 as the result of work by Lord Holford, a part-time member of the Central Electricity Generating Board (National Grid's predecessor). The Holford Rules have been augmented by both National Grid and SHE Transmission plc to reflect environmental legislation and best practice in recent years. We have continued to use them as a valuable set of guidelines for reducing the impact of our assets on landscapes. The guidance recommends appropriate application of the Holford Rules to inform routeing. These rules advocate the application of a hierarchical approach to routeing which first avoids major areas of highest amenity, then smaller areas of high amenity, and finally considers factors such as backdrop, woodland and orientation. The Holford Rules apply the term ‘amenity’ to refer to environmental designations and classifications such as Natura 2000 sites, Sites of Special Scientific Interest (SSSI), Scheduled Monuments, Listed Buildings, National Parks.The guidance also recognises that the key effect of overhead lines is visual and it advises that the routeing of overhead lines should consider the types of mitigation (screening) that could offset any visual effects. In their National Policy Statement EN-5, the Government has stated that the Holford Rules “should be followed by developers when designing their proposals.” Their use is therefore Government policy, rather than a voluntary choice of SHE Transmission plc.

SHE Transmission are regulated by the Office for Gas and Electricity Markets (Ofgem), the regulator responsible for representing consumers' interests. Electricity consumer interests are therefore one of our key drivers and this is enshrined in our statutory duties under the Electricity Act.

In particular we have a statutory duty to develop, maintain and operate an efficient, economic and co-ordinated transmission system. Since the costs of these projects will ultimately be paid for by electricity consumers, we have a responsibility to take cost into account with due weighting in a comparison against other important factors.

It’s the highest voltage electricity network in the UK – the ‘motorway network’ of the energy world. It transmits large quantities of electricity over long distances via wires carried on a system of mainly metal towers (pylons) and large substations. Transmission voltages in Scotland are 132kV, 275kV and 400kV. Larger generation schemes usually connect to the Transmission system.

The lower voltage parts of the system are called distribution networks. In Scotland, these local networks operate below 132kV whereas in England the distribution network includes 132kV.

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